Magnetism and matter.

two magnets have the same length and the same pole strength,but one of the magnets has a small hole at is center.then

• both have equal magnetic moment

• one with hole has small magnetic moment.

• one with hole has large magnetic moment.

• one with hole loses magnetism through the hole

A large magnet is broken into two pieces so that the lengths are in the ratio 2:1.the pole strength of the two pieces will have ratio

• 2 : 1

• 1:2

• 4:1

• 1:1

work done in rotating a bar magnet from 0 to 120 $\degree$  is 

•  $\frac{1}{2}$  MB

•  $\frac{3}{2}$  MB

• MB

•  $\frac{2}{3}$  MB

Gauss law for magnetism is

• the net magnetic flux through any closed surface is B. $\Delta$ s

• the net magnetic flux through any closed surface is E. $\Delta$ s

• the net magnetic flux through any closed surface is zero

• both a and c

At a place angle of dip is 30 $\degree$ .If horizontal component of earths magnetic field is H,then the total intensity of magnetic field will be 

•  $\frac{H}{2}$  

•  $\frac{2H}{\sqrt{3}}$  

• 2H

• H $\sqrt{\frac{3}{2}}$  

the value of angle of dip is zero at the magnetic equator because on it

• V and H are equal

• V and H are zero

• V is zero

• H is zero

The relative permeability of a substance x is slightly less than unity and that of substance y is slightly more than unity,then

• x is paramagnetic and y is ferromagnetic

• x is diamagnetic and y is ferromagnetic

• x and y are paramagnetic

• x is diamagnetic and y is paramagnetic

In a permanent magnet at room temperature

• magnetic moment of each molecule is zero

• the individual molecules have non zero magnetic moment which are all perfectly aligned

• domains are partially aligned

• domains are perfectly aligned

Hysteresis loss is minimized by using

• alloy of steel

• shell type of core

• thick wire which has low resistance

• metal

To make electromagnet, substance should be

• high permeability and high susceptibility

• low permeability and high susceptibility

• high permeability and low susceptibility

• low permeability and low susceptibility